Thanks to modern computers and software the old, 'official' Voyager Jupiter images can be reprocessed into something much better. There is also a lot of Voyager data there that was never processed into color composites and/or mosaics (or at least it has not appeared on the WWW). With proper processing the apparent image quality approaches the quality of the Cassini images but needless to say the wavelength coverage is (vastly) inferior.

I have recently been taking a close look at the high resolution Voyager 1 images, i.e. the images obtained in early March 1979. This is going to result in some new and/or reprocessed mosaics. The first one is now complete and I'm working on another one.

The image below is a 12 image mosaic (12 orange + 12 violet + 12 synthetic green images). The images were obtained on March 2, 1979 at a range of 4.3 million km. The first image (C1629045.IMQ) was obtained at 05:09:23 and the last one (C1629131.IMQ) at 05:46:11. The resolution is roughly 43 km/pixel.

The raw images were calibrated, reprojected to simple cylindrical projection, mosaicked and then rendered using a typical viewing geometry (there is no such thing as a "correct viewing geometry" because the images were obtained over a 37 minute period with Jupiter rotating). I then fixed the color balance. I still haven't 'standardized' how I process the Voyager color. I wasn't completely satisfied with the color I got using an approach similar to what's described in another thread but I think the color could be improved a bit. The final step was to sharpen the resulting image a bit, mainly to compensate for all of the resampling that the previous processing steps required.

This image shows lots of features: The Great Red Spot and one of the three white ovals present during the Voyager flybys, smaller spots, scallopped belt/zone boundaries, gravity waves, a bright equatorial plume and the dusky south polar region.

I don't think I'm bragging by saying that this is probably the best Voyager 1 Jupiter mosaic that I know of, mainly because of its size (12 images).

I will be posting more Jupiter stuff in this thread in the coming days/weeks, both mosaics and interesting images (and needless to say, others are welcome to post images and mosaics as well).

I don't think I'm bragging by saying that this is probably the best Voyager 1 Jupiter mosaic that I know of, mainly because of its size (12 images).

You have every right to brag as this is the best Voyager Jupiter product I've seen. The resolution and image quality reminds of New Horizons LORRI images and yet the colors remind of Cassini. With the filter set you had to work with, I think the color looks great.

Taking Bjorn's awesome image above as "reference", I created a blink animation that compares it to a Galileo image of the Great Red Spot almost 20 years later.

The Galileo image had used a synthetic green channel, so I adjusted the colors to match closest to Bjorn's image. I also took some liberties with warping and resizing the Galileo image to match Bjorn's image. I wanted to highlight structural, not color or size differences.

[Animated GIF: click to animate]

In the Galileo 1996 image, the clear zone to the S of the GRS is much thinner. The S belt also seems less affected by the GRS. Interestingly, the thin red band to the SE (standing wave?) is present in both images. There is also much more chaos in the region to the NE. In the Voyager 1 image, the NE section shows a smoother transition between zones.

Fantastic pic! Did you use ISIS? If so, what were your processing steps?

I didn't use ISIS. Voyager calibration isn't available yet in ISIS 3 and ISIS 2 doesn't work properly on my computer. I think I now know why but I didn't when I made the mosaic.

QUOTE (tedstryk @ Aug 20 2010, 10:08 PM)

Awesome. Voyager images are quite good once you remove the gunk.

Yes, that's my experience as well. The problem is that this wasn't done carefully enough ~30 years ago so those old, 'official' color composites and mosaics really need to be reprocessed.

QUOTE (antipode @ Aug 21 2010, 11:10 PM)

Are we seeing cloud shadows new the top of the image?

I don't think so. You need higher resolution and/or lower solar elevation angles (mainly the former) for cloud shadows/vertical relief to become apparent. Vertical relief (if one can speak of that in the context of gaseous planets) is visible in higher resolution images but it is usually not obvious unless the images are sharpened. Incidentally, the Voyager images are better than the Galileo images if you are interested in cloud shadows and vertical relief. The highest reolution Voyager images are of higher resolution than the Galileo images. In addition, compression artifacts can be an issue if you want to examine small scale features in the Galileo images.

Actually I now think (after taking a careful look at lots of Voyager images) that the Voyager dataset still is in some ways better than the Galileo dataset. While the Galileo images are more carefully targeted and the wavelength coverage is far better (near infrared filters) the Voyager images have no compression artifacts, there is a significant amount of images of higher resolution than anything Galileo obtained and the Voyager images are a better data source for atmospheric movies. So if you are interested in very small scale details in the Jovian atmosphere the Voyager 1 images are what you want.

I'm currently working on another 12 image mosaic that should be finished soon, possibly this week.

Yes, that's my experience as well. The problem is that this wasn't done carefully enough ~30 years ago so those old, 'official' color composites and mosaics really need to be reprocessed.

Even when they did go through the proper steps, doing all the steps with the 8 bit data rather than converting to 16 bit, something beyond the capability of the vax computers they were using, really degraded the images.

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